There may be several causes for hand pain. Specially at that age. It may be pain due to arthritis , pain due to injury or just pain due to improper positioning of hand or over use of hand , worst cases it might be due to other injuries also.
Next Steps
Apply ice pack / cold pack which might help reducing pain and swelling during initial stages. Try applying topical creams to soothe muscular pain if you feel that the pain is muscular , but usually it subsides in a month if pain is prolonged please check if it is result of arthritis or any other injury
Health Tips
Please provide further information like history and other variations like arthritis or any other problems pertaining to bone or muscle that might help
To resolve your problem in a better manner. Be Healthy.